A Tube Stereo Amplifier, From Scratch

November 20, 2024 by 16 Comments

A conventional tube amplifier has a circuit whose fundamentals were well in place around a hundred years ago, so there are few surprises to be found in building one today. Nevertheless, building one is still a challenge, as [Mike Freda shows us with a stereo amplifier in the video below the break.

The tubes in question are the 12AU7 double triode and 6L6 tetrode, in this case brand new PSVANE parts from China. The design is a very conventional single-ended class A circuit, with both side of the double triode being used for extra gain driving the tetrode. The output uses a tapped transformer with the tap going to the other grid in the tertode, something we dimly remember as being an “ultra-linear” circuit.

There’s an element of workshop entertainment in the video, but aside from that we think it’s the process of characterising the amp and getting its voltages right which is the take-away here. It’s not something many of us do these days, so despite the apparent simplicity of the circuit it’s worth a look.

These modern tubes come from a variety of different sources, we’ve attempted to track them down in the past.

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An image of a black carabiner-esque frame surrounding a round, yellow bezeled digital watch. A black paracord lanyard is attached to the top right of the black frame and a yellow button is visible near the top left of the frame.

A Cyberpunk Pocketwatch

November 20, 2024 by 20 Comments

For a time, pocketwatches were all the rage, but they were eventually supplanted by the wristwatch. [abe] built this cyberpunk Lock’n’Watch to explore an alternate history for the once trendy device.

The build was inspired by the chunky looks of Casio sport watches and other plastic consumer electronics from the 1980s and 90s. The electronics portion of this project relies heavily on a 1.28″ Seeed Studio Round Display and a Raspberry Pi 2040 XIAO microcontroller board. The final product features a faux segmented display for information in almost the same color scheme as your favorite website.

[abe] spent a good deal of the time on this project iterating on the bezel and case to hold the electronics in this delightfully anachronistic enclosure. We appreciated the brief aside on the philosophical differences between Blender, TinkerCAD, and Fusion360. Once everything was assembled, he walks us through some of joys of debugging hardware issues with a screen flicker problem. We think the end result really fulfills the vision of a 1980s pocketwatch and that it might be just the thing to go with your cyberdeck.

We’ve seen accelerometers stuffed into old pocketwatch cases, a more useful smart pocketwatch, or you could learn how to repair and restore vintage watches.

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[James] and his Lemontron portable 3D printer

If Life Gives You Lemons, Build This Lemontron

November 20, 2024 by 12 Comments

What if your 3D printer could fit in a box of filament but still rival the build plate size of heavyweights? Enter the Lemontron, a free and open source portable printer making waves in the maker community for its compact form factor and budget-friendly price. Watch [James]’ video on his build story here. Built around the Positron drive—a unique mechanism introduced by [Kralyn] in 2022—the Lemontron is the latest evolution of this innovative design. Although Kralyn mysteriously disappeared, their work inspired other projects like the Positron JourneyMaker and this Lemontron.

The Lemontron started as a unibody chassis mod for the JourneyMaker but grew into a complete redesign, cutting costs in half without sacrificing performance. By eliminating expensive CNC parts, it’s entirely made from off-the-shelf components, bringing the build cost to just $413. Compare that to $800 for the JourneyMaker and $699 for the Positron v3.2 kit.

Overhead photo of [James]' hands assembling the Lemontron Portable 3D printerRecent video updates show the Lemontron in action, printing impressively large and complex models. It tackled a marble run with 80-degree unsupported overhangs and a ‘comically large’ Benchy, proving its capability. Its compact design, paired with robust performance, is an exciting alternative for tinkerers seeking quality on a budget.

The Lemontron is in its final development stages, with frequent updates dropping on its YouTube channel. If you’re in the market for a more “traditional” mini-printer, check out this cool suitcase model from 2014.

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With Core ONE, Prusa’s Open Source Hardware Dream Quietly Dies

November 20, 2024 by 151 Comments

Yesterday, Prusa Research officially unveiled their next printer, the Core ONE. Going over the features and capabilities of this new machine, it’s clear that Prusa has kept a close eye on the rapidly changing desktop 3D printer market and designed a machine to better position themselves within a field of increasingly capable machines from other manufacturers.

While some saw the incremental upgrades of the i3 MK4 as being too conservative, the Core ONE ticks all the boxes of what today’s consumer is looking for — namely high-speed CoreXY movement with a fully enclosed chamber — while still offering the build quality, upgradability, and support that the company has built its reputation on. Put simply it’s one of the most exciting products they’ve introduced in a long time, and exactly the kind of machine that many Prusa fans have been waiting for.

Unfortunately, there’s one feature that’s ominously absent from the Core ONE announcement post. It’s easy to overlook, and indeed, most consumers probably won’t even know it’s missing. But for those of us who are concerned with such matters, it’s an unspoken confirmation that an era has finally come to an end.

With the Core ONE, Prusa Research is no longer in the business of making open source 3D printer hardware, but that doesn’t mean that the printer isn’t hackable. It’s complicated, so read on.

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FreeCAD Version 1.0 Released

November 20, 2024 by 35 Comments

After 22 years of development, FreeCAD has at long last reached the milestone of version 1.0. On this momentous occasion, it’s good to remember what a version 1.0 is supposed to mean, as also highlighted in the release blog post: FreeCAD is now considered stable and ready for ‘real work’. One of the most important changes here is that the topological naming problem (TNP) that has plagued FreeCAD since its inception has now finally been addressed using Realthunders’ mitigation algorithm, which puts it closer to parity here with other CAD packages. The other major change is that assemblies are now supported with the assembly workbench, which uses the Ondsel solver.

Other changes include an updated user interface and other features that should make using FreeCAD easier and closer in line with industry standards. In the run-up to the 1.0 release we already addressed the nightmare that is chamfering in FreeCAD, and the many overlapping-yet-uniquely-incomplete workbenches, much of which should be far less of a confabulated nightmare in this bright new 1.0 future.

Naturally, the big zero behind the major version number also means that there will still be plenty of issues to fix and bugs to hunt down, but it’s a promising point of progress in the development of this OSS CAD package.

Boss Byproducts: Calthemites Are Man-Made Cave Dwellers

November 20, 2024 by 6 Comments
Some lovely orange calthemite flowstone colored so by iron oxide from rusting steel reinforcing.
Some lovely orange calthemite flowstone colored so by iron oxide from rusting steel reinforcing. Image via Wikipedia

At this point, we’ve learned about man-made byproducts and nature-made byproducts. But how about one that’s a little of both? I’m talking about calthemites, which are secondary deposits that form in those man-made caves such as parking garages, mines, and tunnels.

Calthemites grow both on and under these structures in forms that mimic natural cave speleothems like stalactites, stalagmites, flowstone, and so on. They are often the result of an hyperalkalinic solution of pH 9-14 seeping through a concrete structure to the point of coming into contact with the air on the underside. Here, carbon dioxide in the air facilitates the necessary reactions to secondarily deposit calcium carbonate.

These calcium carbonate deposits are usually white, but can be colored red, orange, or yellow thanks to iron oxide. If copper pipes are around, copper oxide can cause calthemites to be blue or green. As pretty as all that sounds, I didn’t find any evidence of these parking garage growths having been turned into jewelry. So there’s your million-dollar idea.

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